Eighteen families living on one side of Ruston Mews off Ladbroke Grove have banded together to draw up plans to give each of their homes a matching two-bedroom roof extension.

It is believed that the project is the largest-ever joint home extension scheme to have been put together by a group of London neighbours, who agreed on a design democratically after being presented with a series of different options for the design of the extension and the materials to use.

Collaborating in this way has numerous advantages, both financial and practical, saving on the cost of fees and making planning permission more likely.

“The issue is that the residents love the area and their community, but their houses are very long and narrow — basically they are small,” says Renée Searle, a director of Threefold Architects, which drew up the plans for the Ruston Mews families.

“The residents wanted to stay in the area, but they also wanted to have a bit more space.”

One of the residents, who asked not to be named, explained that making a communal planning application would save money and give them a greater chance of success.

Each family has budgeted up to £1,500 each to spend on professional fees to draw up the plans and take them through the planning system. Their money has been put into a joint bank account for security.

If planning consent is obtained, each resident will pay an estimated £70,000 to £80,000 for their extension.

“The cost of moving to a larger property and the moving costs would be much, much more than that,” explained the resident.

She also hopes that the joint application will help persuade planners to rule in favour of the project.

“A multiple application is the only way when you have houses with an unbroken roof line because the council will not approve single applications to change just one house,” she said.

The terrace houses are on the north side of the mews and were built in the Seventies.

The owners hope to add a metal-clad roof extension — which will be prefabricated off-site and erected within four weeks — turning the current two-bedroom homes into four-bedroom houses, considerably adding to their value.

Kensington and Chelsea council is due to rule on the plans later this year.